Association is an optional initial ranging procedure occurring during scanning interval with respect to one of the neighbor Base Stations (BSs). The function of association is to enable the Mobile Station (MS) to acquire and record ranging parameters and service availability information for the purpose of proper selection of Handover (HO) target and/or expediting a potential future HO to a target BS.
There are three levels of association: Association Level 0, Association Level 1 and Association Level 2. Association Level 1 and Association Level 2 are mainly related in the following.
Before performing association, if the serving BS decides to recommend that the MS scan neighbor BSs with Association Level 1 or Association Level 2, it should first request association ranging information to the requested neighbor stations, i.e. an association parameter negotiation is needed. If the requested neighbor station can provide enough resource during the association parameter negotiation procedure, the MS will be allocated the association parameters including rendezvous time, CDMA code, and transmission opportunity offset. If there is no enough resource allocated, the MS may perform the Association Level 0 and then the association ranging parameters can not be allocated.
In Association Level 1 or Level 2, each neighbor BS to be associated by the MS pre-allocates a unique initial CDMA code and a transmission opportunity offset for the MS, and sends the unique initial CDMA code and the transmission opportunity offset to the serving BS via a backbone network. The serving BS coordinates to assure that the neighbor BSs do not overlap in ranging regions or too close in transmission times. The rendezvous time is a frame offset value which equals the difference between the frame number for the recommended association neighbor BS providing the MS with the dedicated ranging transmission opportunity and the frame number for the serving BS sending an MOB_SCN-RSP message.
The association parameters obtained during association parameter negotiation procedure are provided for the MS by the serving BS via the MOB_SCN-RSP message. In a multi-hop radio relay communication system, an MS may access a Relay Station (RS) to enter the network, i.e. the associated neighbor station may be an RS. However, there is no association method for the associated neighbor station being an RS in the prior art. In addition, if the associated RS can schedule the association parameters independently, the serving BS of the associated RS may not acquire the association parameters of the associated RS. In this case, the association parameter negotiation via the backbone network in the prior art can not satisfy the requirements of Association Level 1 and Association Level 2.